Degradable anchor device with retained granular material

ABSTRACT

Therefore in one aspect, an anchoring device is disclosed, including: a degradable substrate with a first hardness wherein an outer extent of the degradable surface includes at least one retaining feature; and a granular gripping material associated with the outer extent of the degradable substrate and the at least one retaining feature, wherein the at least one retaining feature retains the granular gripping material and the granular gripping material has a second hardness greater than the first hardness. In certain embodiments, the at least one retaining feature is at least one bump ring. In certain embodiments, the at least one bump ring is at least one segmented bump ring. In certain embodiments, the at least one retaining feature is at least one helical feature. In certain embodiments, the at least one retaining feature is at least one knurled region. In certain embodiments, the degradable substrate includes a leading protrusion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a Continuation-In-Part Application of U.S.Non-Provisional patent application Ser. No. 14/561,523, filed Dec. 5,2014 which is incorporated herein by reference in its entirety.

BACKGROUND

1. Field of the Disclosure

This disclosure relates generally to degradable slip rings and systemsthat utilize same for downhole applications.

2. Background of the Art

Wellbores are drilled in subsurface formations for the production ofhydrocarbons (oil and gas). Hydrocarbons are trapped in various traps orzones in the subsurface formations at different depths. In manyoperations, such as fracturing, it is required to anchor devices (suchas packers, bridge plugs, etc.) in a downhole location to facilitateproduction of oil and gas. After such operations, anchoring devices mustbe removed or destroyed before following operations can begin. Suchremoval operations may be costly and/or time consuming. It is desired toprovide an anchoring device that can provide sufficient anchoringperformance while providing desired and predictable degradationcharacteristics.

The disclosure herein provides controlled degradable slip rings andsystems using the same for downhole applications.

SUMMARY

In one aspect, an anchoring device is disclosed, including: a degradablesubstrate with a first hardness wherein an outer extent of thedegradable surface includes at least one retaining feature; and agranular gripping material associated with the outer extent of thedegradable substrate and the at least one retaining feature, wherein theat least one retaining feature retains the granular gripping materialand the granular gripping material has a second hardness greater thanthe first hardness.

In another aspect, a method to anchor a downhole device is disclosed,including: providing a degradable substrate with a first hardness,wherein an outer extent of the degradable surface includes at least oneretaining feature; applying a granular gripping material to the outerextent of the degradable substrate and the at least one retainingfeature, wherein the granular gripping material has a second hardnessgreater than the first hardness; and retaining the granular grippingmaterial via the at least one retaining feature.

In another aspect, a downhole system is disclosed, including: a casingstring; and an anchoring device associated with the casing string,including: a degradable substrate with a first hardness, wherein anouter extent of the degradable surface includes at least one retainingfeature; and a granular gripping material associated with the outerextent of the degradable substrate and the at least one retainingfeature, wherein the at least one retaining feature retains the granulargripping material and the granular gripping material has a secondhardness greater than the first hardness.

Examples of certain features of the apparatus and method disclosedherein are summarized rather broadly in order that the detaileddescription thereof that follows may be better understood. There are, ofcourse, additional features of the apparatus and method disclosedhereinafter that will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure herein is best understood with reference to theaccompanying figures, wherein like numerals have generally been assignedto like elements and in which:

FIG. 1 is a schematic diagram of an exemplary drilling system thatincludes downhole elements according to embodiments of the disclosure;

FIG. 2 is a schematic diagram of an exemplary downhole device for use ina downhole system, such as the one shown in FIG. 1, according to oneembodiment of the disclosure;

FIG. 3A shows a partial view of the substrate of an exemplary anchoringdevice for use with a downhole device, such as the downhole device shownin FIG. 2 for use with a downhole system, according to one embodiment ofthe disclosure;

FIG. 3B shows a partial cross sectional view of the anchoring deviceshown in FIG. 3A;

FIG. 3C shows a partial cross sectional view of the anchoring deviceshown in FIG. 3A with a granular gripping material;

FIG. 4A shows a partial view of the substrate of another exemplaryanchoring device for use with a downhole device, such as the downholedevice shown in FIG. 2 for use with a downhole system, according to oneembodiment of the disclosure;

FIG. 4B shows a partial view of the substrate of another exemplaryanchoring device for use with a downhole device, such as the downholedevice shown in FIG. 2 for use with a downhole system, according to oneembodiment of the disclosure;

FIG. 4C shows a partial view of the substrate of another exemplaryanchoring device for use with a downhole device, such as the downholedevice shown in FIG. 2 for use with a downhole system, according to oneembodiment of the disclosure; and

FIG. 4D shows a partial view of the substrate of another exemplaryanchoring device for use with a downhole device, such as the downholedevice shown in FIG. 2 for use with a downhole system, according to oneembodiment of the disclosure.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows an exemplary embodiment of a downhole system to facilitatethe production of oil and gas. In certain embodiments, system 100 allowsfor fracturing operations to facilitate production of oil and gas.System 100 includes a wellbore 106 formed in formation 104 with casing108 disposed therein.

In an exemplary embodiment, a wellbore 106 is drilled from a surface 102to a downhole location 110. Casing 108 may be disposed within wellbore106 to facilitate production. In an exemplary embodiment, casing 108 isdisposed through multiple zones of production Z1 . . . Zn in a downholelocation 110. Wellbore 106 may be a vertical wellbore, a horizontalwellbore, a deviated wellbore or any other suitable type of wellbore orany combination thereof.

To facilitate downhole operations, such as fracturing operations, bridgeplugs 116 a, packers 116 b, or other suitable downhole devices areutilized within casing string 108. In certain embodiments, such downholedevices 116 a,b are anchored to casing string 108 via an anchor assembly118. In certain embodiments, bridge plugs 116 a utilize an anchorassembly 118 and frac balls 120 to isolate zones Z1 . . . Zn forfracturing operations. In certain embodiments, frac balls 120 aredisposed at a downhole location 110 to obstruct and seal fluid flow inlocal zone 112 to facilitate flow to perforations 114 in conjunctionwith bridge plugs 116 a. In certain embodiments, packers 116 b areutilized in conjunction with anchor assembly 118 to isolate zones Z1 . .. Zn for fracturing operations.

In certain embodiments, frac fluid 124 is pumped from a frac fluidsource 122 to a downhole location 110 to flow through perforations 114in a zone 112 isolated by downhole device 116 a,b. Advantageously,fracturing operations allow for more oil and gas available forproduction.

After desired operations (such as fracturing operations) and beforefollowing operations, anchoring devices 118 are often removed orotherwise destroyed to allow the flow of oil and gas through casing 108.In an exemplary embodiment, anchoring devices 118 are configured toanchor against casing 108 of local zone 112 until a predetermined timeat which anchoring devices 118 dissolve or degrade to facilitate theproduction of oil and gas. Advantageously, in an exemplary embodiment,the anchoring devices 118 herein are formed of multiple materials tohave predictable and adjustable degradation characteristics whileallowing for suitable anchoring characteristics.

FIG. 2 shows a downhole device 216, such as a bridge plug, packer, orany other suitable downhole device, for use downhole systems such as thesystem 100 shown in FIG. 1. In an exemplary embodiment, downhole system200 includes downhole device 216 interfacing with casing 208 via anchorassembly 218 to anchor a downhole device 216. In certain embodiments, afrac ball 220 is used with downhole device 216 to isolate frac fluidflow within the wellbore.

In an exemplary embodiment, anchor assembly 218 includes a wedge 224 anda slip ring 228. In certain embodiments, wedge 224 is forced downhole toforce slip ring 228 outward against casing 208 to anchor against casing208. In certain embodiments, slip ring 228 can crack or otherwiseseparate as it is driven against casing 208. In certain embodiments,wedge 224 is forced via a setting tool, explosives, or any othersuitable means. In certain embodiments, downhole device 216 furtherutilizes a sealing member 226 to seal downhole device 216 against casing208 and further resist movement. Sealing member 226 may similarly bedriven toward casing 208 via wedge 224.

In an exemplary embodiment, a substrate of a slip ring 228 is formed ofa degradable material to allow slip ring 228 to dissolve or degradeafter a desired anchoring function is performed. In certain embodiments,a secondary material is used in conjunction with the substrate of theslip ring 228 to anchor the slip ring 228 against casing 208. Typically,a secondary material is harder than casing 208 to allow slip ring 228 topartially embed in casing 208. In certain embodiments, the downholetemperature exposure to downhole device 216 and slip ring 228 variesfrom 100 to 350 degrees Fahrenheit at a particular downhole location fora given area. Advantageously, slip ring 228 as described herein mayallow for degradation after a desired time in certain downholeenvironments, while allowing suitable anchoring performance. In certainembodiments, portions of slip ring 228 can degrade or otherwise notprevent further downhole operations or restrict flow within a wellbore.

FIGS. 3A, 3B and 3C show an exemplary embodiment of slip ring 328. In anexemplary embodiment, slip ring 328 includes a substrate 331 and agranular gripping material 330. In certain embodiments, slip ring 328 isused with downhole devices as shown in FIG. 2 to anchor the downholedevices against a casing. Advantageously, slip ring 328 is a degradabledevice, allowing slip ring 328 to degrade without any secondary removalor destruction operations.

In an exemplary embodiment, substrate 331 is a degradable material.Advantageously, by forming substrate 331 of slip ring 328 from adegradable material, a downhole device may be anchored by slip ring 328for the desired period of time, and then the slip ring 328 may bedisintegrated to allow further operations without any obstructions. Incertain embodiments, substrate 331 is formed from a corrodible metalsuch as a controlled electrolytic metallic, including but not limited toIntallic. Substrate 331 materials may include: a magnesium alloy, amagnesium silicon alloy, a magnesium aluminum alloy, a magnesium zincalloy, a magnesium manganese alloy, a magnesium aluminum zinc alloy, amagnesium aluminum manganese alloy, a magnesium zinc zirconium alloy,and a magnesium rare earth element alloy. Rare earth elements mayinclude, but is not limited to scandium, yttrium, lanthanum, cerium,praseodymium, neodymium, and erbium. In certain embodiments, substratematerials 331 are further coated with aluminum, nickel, iron, tungsten,copper, cobalt. In certain embodiments, substrate 331 materials areconsolidated and forged. In certain embodiments, the elements can beformed into a powder and a substrate can be formed from pressed powder.In an exemplary embodiment, the material of substrate 331 is selectedbased on desired degradation characteristics of slip ring 328.

In an exemplary embodiment, substrate 331 forms a generally cylindricalshape with an inner extent 336 and an outer extent 334. In certainembodiments, inner extent 336 has a reducing or reduced radius portionto allow a downhole device to be retained within the slip ring 328. Inan exemplary embodiment, the material of substrate 331 is chosen withrespect to the relative hardness of the downhole device to preventdamage to the downhole device. In an exemplary embodiment, outer extent334 of slip ring 328 is configured to interface with a casing. In anexemplary embodiment, outer extent 334 includes granular grippingmaterial 330 designed to interface with casing.

In an exemplary embodiment, slip ring 328 can be configured to break into several sections when expanded. In certain embodiments, slip ring 328can be expanded by a wedge as previously shown in FIG. 2. In order tofacilitate fracturing of slip ring 328 certain embodiments of slip ring328 include crack initiation points 332 disposed on outer extent 334.Crack initiation points 332 include, but are not limited to cuts,grooves, slits, perforations, etc. Crack initiation points 332 may serveas a stress concentration point to initiate cracking, fracturing, orseparation along the longitudinal axis of slip ring 328 as slip ring 328is expanded. In certain embodiments, crack initiation points 332 areformed via electrical discharge machining substrate 331.

In an exemplary embodiment, outer extent 334 includes granular grippingmaterial 330 configured to interface with a casing or other suitableanchor medium. In an exemplary embodiment, the material of granulargripping material 330 is selected to be harder than the interfacingcasing. In other embodiments, the material of the granular grippingmaterial 330 is the same hardness or softer than the interfacing casing.Casing may have a hardness of approximately 120 ksi. Casing grades mayrange from L80 to Q125. Advantageously, a relatively harder anchorgranular gripping material 330 allows for granular gripping material 330to firmly anchor the downhole device to casing or other suitable anchormedium. In other embodiments, granular gripping material 330 utilizesfriction and casing irregularities to interface with a casing or othersuitable anchor medium. In certain embodiments, anchor granular grippingmaterial 330 is formed of a harder material than substrate 331.Advantageously, materials, particularly degradable materials, may nothave a suitable hardness to adequately anchor to a casing or othersuitable anchor material, requiring the use of a harder anchor granulargripping material 330 as described herein. Materials selected forsubstrate 331 and granular gripping material 330 may be carefullyselected to ensure gripping material 330 embeds further into a casing oranchor medium compared to substrate 331.

In an exemplary embodiment, granular gripping materials 330 are on theouter extent 334 of slip ring 328. In certain embodiments, granulargripping materials 330 are disposed in undercut portion 338.Advantageously, a large portion of slip ring 328 may be covered withgranular gripping materials 330 to allow for greater anchoringperformance. In certain embodiments, by covering a large portion of slipring 328 the substrate 331 of slip ring 328 can avoid or mitigatedamage. Advantageously, by utilizing granular gripping materials 330, asubstrate 331 can be formed with a lower strength material to allow forgreater ductility of slip ring 328. In an exemplary embodiment, granulargripping materials 330 can be generally granular form of similar sizesand of regular or irregular shapes. In certain embodiments, granulargripping materials 330 a can be relatively larger. In other embodiments,granular gripping materials 330 b can be relatively smaller compared toother granular gripping materials 330 a. As shown in FIG. 3C the grainsize of granular material 330 a,330 b may vary based on application. Incertain embodiments, granular material 330 a,330 b is applied to slipring 328 in multiple layers. Advantageously, the use of multiple layersof granular material 330 a,330 b can prevent damage to substrate 331 bydistributing anchor forces and allowing harder materials (or largergranular materials) 330 a to interface with casing or anchor medium,while softer granular materials (or smaller granular materials) 330 binterface with substrate 331. In certain embodiments, materials 330 ainterfacing with casing or anchor medium have a granule size of 0.5 to10 mm. In an embodiment materials 330 a interfacing with casing oranchor medium have a granule size of 1 to 5 mm. In certain embodiments,materials 330 b interfacing with substrate 331 have a granule size of 1micron to 2 mm. In an embodiment, materials 330 b interfacing withsubstrate 331 have a granule size of 50 micron to 1 mm. In certainembodiments, the combined thickness of layers 330 a,330 b ranges from0.5 to 10 mm. In an embodiment, the combined thickness of layers 330a,330 b ranges from 2 to 5 mm. Further, the characteristics andperformance of slip ring 328 can be adjusted and designed by alteringthe layers 330 a,b in relation to substrate 331 and casing or anchormedium. Advantageously, granular gripping materials 330 may beconfigured to be sized and shaped to allow passage through intended flowpaths and to allow operations to continue after a substrate 331 hasdissolved.

In an exemplary embodiment, granular gripping materials 330 are formedfrom disintegrable materials that disintegrate into small particulates.Granular gripping materials 330 can be formed of any suitable material,including, but not limited to oxides, carbides, and nitrides. In certainembodiments, granular gripping materials 330 are formed from aluminumoxide, silicon carbide, tungsten carbide, zirconium dioxide, and siliconnitride. In certain embodiments, granular gripping materials 330 cancontain ceramic type proppants or other high hardness materials.

In an exemplary embodiment, granular gripping materials 330 are disposedin an undercut portion 338 formed in substrate 331. In certainembodiments, undercut portion 338 has a smaller outside diameter thanthe remainder of outer extent 334 to allow the inclusion of granulargripping materials 330 while maintaining the same or similar outsidediameter as the remainder of outer extent 334. Advantageously, undercutportion 338 may ease the application of granular gripping material 330and binder 339.

Granular gripping materials 330 may be attached to substrate 331 via abinder 339 or any other suitable adhesive. In certain embodiments, thebinder utilizes is degradable. Binders include, but are not limited totoughened acrylics, epoxy, low metal point metals (such as aluminum,magnesium, zinc, and their alloys), etc. In other embodiments, undercutportion 338 can retain granular gripping materials 330 without anyadditional components. In certain embodiments, various sizes of granularmaterial 330 a,b are bound by various binders 339 a,b. In certainembodiments, various binders 339 a,b can vary based on size of granularmaterial 330 a,b as well as relative location within slip ring 328.

FIGS. 4A-4D show alternative embodiments of slip ring 428. In anexemplary embodiment, slip ring 428 includes a retaining feature 440formed in substrate 431. In an exemplary embodiment, retaining feature440 can be utilized to retain granular gripping material when slip ring428 is engaged against casing or other suitable surfaces. In certainembodiments, slip ring 428 is used with downhole devices as shown inFIG. 2 to anchor against a casing.

In an exemplary embodiment, outer extent 434 of slip ring 428 includesat least one retaining feature 440 formed in substrate 431. Retainingfeature 440 can be formed to retain a granular gripping material toprevent the unwanted migration of the material, particularly in highpressure and high temperature environments. In certain embodiments,retaining feature 440 can retain granular gripping material when thegranular gripping material is subjected to shear forces and other forcesduring engagement. Advantageously, retaining feature 440 providesadditional surface area for a binder associated with the granulargripping material as well as features to resist sliding of the granulargripping material. Retaining features 440 can include, but are notlimited to protrusions, grooves, surface irregularities, finishes,surface scratches, threading, holes, angled portions, etc. Retainingfeatures 440 can be continuous, discontinuous, patterned, random, etc.

Referring to FIG. 4A, in an exemplary embodiment, retaining feature 440is at least one bump ring to prevent the sliding of granular grippingmaterial. Bump rings can be raised protrusions or groovescircumferentially disposed along the outer extent 434 of slip ring 428.In certain embodiments, bump rings can be of any suitable height,number, pattern, etc. In certain embodiments, bump rings can be disposedat any suitable location.

Referring to FIG. 4B, in an exemplary embodiment, retaining feature 440is at least one segmented bump ring to prevent the sliding of granulargripping material. Segmented bump rings can be raised protrusions orgrooves circumferentially disposed along the outer extent 434 of slipring 428. In certain embodiments, segmented bump rings can be of anysuitable height, number, pattern, etc. In certain embodiments, segmentedbump rings can be disposed at any suitable location. In certainembodiments, segments of bump rings can be randomly disposed.

Referring to FIG. 4C, in an exemplary embodiment, retaining feature 440is helical feature to prevent the sliding of granular gripping material.Helical feature can be raised protrusions or grooves circumferentiallydisposed along the outer extent 434 of slip ring 428. In certainembodiments, helical bump feature can be of any suitable height, number,pattern, etc. In certain embodiments, helical features can a continuoushelical shape or a segmented helical shape be disposed at any suitablelocation along outer extent 434 of slip ring 428. In certainembodiments, segments of helical features can be randomly disposed.

Referring to FIG. 4D, in other embodiments, retaining feature 440 is aknurled or rough surface portion disposed along outer extent 434 of slipring 428. In certain embodiments, a knurled, rough, or other treatmentportion can be formed in substrate 431 and disposed circumferentially,axially, etc. In certain embodiments, surface treatments can be of anysuitable width, depth, pattern, roughness, etc. In certain embodiments,retaining feature 440 can include either bump rings or surfacetreatments in multiple locations, a combination of retaining features440, or any other suitable retaining feature 440 to retain the granulargripping material.

In an exemplary embodiment, retaining feature 440 can be integrallyformed in substrate 431. Retaining feature 440 can be formed viacasting, machining, or any other suitable forming technique. In certainembodiments, retaining feature 440 can be formed after other portions ofslip ring 428 are formed.

In certain embodiments, slip ring 428 includes a leading protrusion 442formed in substrate 431. Leading protrusion 442 may be disposed on theouter extent 434 of a downhole edge of slip ring 428. During operation,a cone or other suitable device can impart a force upon inner extent 436to expand slip ring 428 along crack initiation points 432.Advantageously, leading protrusion 442 can limit expansion and travel ofslip ring 428 during use by contacting the inner walls of the casingbefore other portions of slip ring 428. The expansion and travel of slipring 428 can be modified by adjusting the radius, width, and otherparameters of leading protrusion 442. In certain embodiments, leadingprotrusion 442 can further be utilized to retain granular grippingmaterial either alone, or in conjunction with retaining feature 440.

Therefore in one aspect, an anchoring device is disclosed, including: adegradable substrate with a first hardness wherein an outer extent ofthe degradable surface includes at least one retaining feature; and agranular gripping material associated with the outer extent of thedegradable substrate and the at least one retaining feature, wherein theat least one retaining feature retains the granular gripping materialand the granular gripping material has a second hardness greater thanthe first hardness. In certain embodiments, the at least one retainingfeature is at least one bump ring. In certain embodiments, the at leastone bump ring is at least one segmented bump ring. In certainembodiments, the at least one retaining feature is at least one helicalfeature. In certain embodiments, the at least one retaining feature isat least one knurled region. In certain embodiments, the degradablesubstrate includes a leading protrusion. In certain embodiments, theleading protrusion limits an engagement depth of the anchoring device.In certain embodiments, the leading protrusion retains the granulargripping material.

In another aspect, a method to anchor a downhole device is disclosed,including: providing a degradable substrate with a first hardness,wherein an outer extent of the degradable surface includes at least oneretaining feature; applying a granular gripping material to the outerextent of the degradable substrate and the at least one retainingfeature, wherein the granular gripping material has a second hardnessgreater than the first hardness; and retaining the granular grippingmaterial via the at least one retaining feature. In certain embodiments,the at least one retaining feature is at least one bump ring. In certainembodiments, the at least one bump ring is at least one segmented bumpring. In certain embodiments, the at least one retaining feature is atleast one helical feature. In certain embodiments, the at least oneretaining feature is at least one knurled region. In certainembodiments, the degradable substrate includes a leading protrusion.

In another aspect, a downhole system is disclosed, including: a casingstring; and an anchoring device associated with the casing string,including: a degradable substrate with a first hardness, wherein anouter extent of the degradable surface includes at least one retainingfeature; and a granular gripping material associated with the outerextent of the degradable substrate and the at least one retainingfeature, wherein the at least one retaining feature retains the granulargripping material and the granular gripping material has a secondhardness greater than the first hardness. In certain embodiments, the atleast one retaining feature is at least one bump ring. In certainembodiments, the at least one bump ring is at least one segmented bumpring. In certain embodiments, the at least one retaining feature is atleast one helical feature. In certain embodiments, the at least oneretaining feature is at least one knurled region. In certainembodiments, the degradable substrate includes a leading protrusion.

The foregoing disclosure is directed to certain specific embodiments forease of explanation. Various changes and modifications to suchembodiments, however, will be apparent to those skilled in the art. Itis intended that all such changes and modifications within the scope andspirit of the appended claims be embraced by the disclosure herein.

1. An anchoring device, comprising: a degradable substrate with a firsthardness, wherein an outer extent of the degradable surface includes atleast one retaining feature; a granular gripping material associatedwith the outer extent of the degradable substrate and the at least oneretaining feature, wherein the at least one retaining feature retainsthe granular gripping material and the granular gripping material has asecond hardness greater than the first hardness.
 2. The anchoring deviceof claim 1, wherein the at least one retaining feature is at least onebump ring.
 3. The anchoring device of claim 2, wherein the at least onebump ring is at least one segmented bump ring.
 4. The anchoring deviceof claim 1, wherein the at least one retaining feature is at least onehelical feature.
 5. The anchoring device of claim 1, wherein the atleast one retaining feature is at least one knurled region.
 6. Theanchoring device of claim 1, wherein the degradable substrate includes aleading protrusion.
 7. The anchoring device of claim 6, wherein theleading protrusion limits an engagement depth of the anchoring device.8. The anchoring device of claim 6, wherein the leading protrusionretains the granular gripping material.
 9. A method to anchor a downholedevice, comprising: providing a degradable substrate with a firsthardness, wherein an outer extent of the degradable surface includes atleast one retaining feature; applying a granular gripping material tothe outer extent of the degradable substrate and the at least oneretaining feature, wherein the granular gripping material has a secondhardness greater than the first hardness; and retaining the granulargripping material via the at least one retaining feature.
 10. The methodof claim 9, wherein the at least one retaining feature is at least onebump ring.
 11. The method of claim 10, wherein the at least one bumpring is at least one segmented bump ring.
 12. The method of claim 9,wherein the at least one retaining feature is at least one helicalfeature.
 13. The method of claim 9, wherein the at least one retainingfeature is at least one knurled region.
 14. The method of claim 9,wherein the degradable substrate includes a leading protrusion.
 15. Adown hole system, comprising: a casing string; and an anchoring deviceassociated with the casing string, comprising: a degradable substratewith a first hardness, wherein an outer extent of the degradable surfaceincludes at least one retaining feature; and a granular grippingmaterial associated with the outer extent of the degradable substrateand the at least one retaining feature, wherein the at least oneretaining feature retains the granular gripping material and thegranular gripping material has a second hardness greater than the firsthardness.
 16. The downhole system of claim 15, wherein the at least oneretaining feature is at least one bump ring.
 17. The downhole system ofclaim 16, wherein the at least one bump ring is at least one segmentedbump ring.
 18. The downhole system of claim 15, wherein the at least oneretaining feature is at least one helical feature.
 19. The downholesystem of claim 15, wherein the at least one retaining feature is atleast one knurled region.
 20. The downhole system of claim 15, whereinthe degradable substrate includes a leading protrusion.